The present invention relates to a method for cleaning and disinfecting a contact lens comprising immersing a contact lens in a treating solution and applying an electric current directly to the treating solution.
A contact lens has some apprehensions that eyes are injured when the contact lens is continuously worn in eyes as it is for a long period of time because stains in the surroundings, microbes, proteins contained in tear fluid, and the like adhere to the contact lens while the contact lens is worn in eyes. Accordingly, there is a necessity to clean or disinfect the contact lens regularly, preferably every day.
As a method for cleaning a contact lens, a method comprising washing the contact lens with a solution containing a surface active agent by fingers has been conventionally known. According to this method, stains on the surface of the contact lens can be removed. However, for instance, when the method is applied to a hard contact lens, there is an apprehension that the hard contact lens is broken or takes scratches during washing. Also, when the method is applied to a water-absorptive soft contact lens, stains such as proteins, which have gotten into the interior of the contact lens, cannot be completely removed. Also, when the water-absorptive soft contact lens is boiled to disinfect in a state that the stains such as proteins, which have gotten into the interior of the lens, are not completely removed, denaturation or coagulation of the proteins having gotten into the contact lens proceeds, and denatured proteins or coagulated proteins are more stiffly adhered to the contact lens. As a result, there occurs a problem of generation of cloudiness of the contact lens.
As a cleaning agent for a contact lens stained with proteins, a cleaning agent containing a proteolytic enzyme has been conventionally known. However, when this cleaning agent is used, although proteins adhered to the surface of the contact lens can be decomposed, it takes a long period of time to obtain cleaning effects. Especially, when the water-absorptive soft contact lens is cleaned by using the cleaning agent, besides taking a long period of time for treating the water-absorptive soft contact lens in comparison with the period of time for treating a hard contact lens, sufficient removing effects of proteins cannot be expected because the proteolytic enzyme itself should go into the interior of a contact lens so that proteins being denatured in the interior of the contact lens can be decomposed.
U.S. Pat. No. 4,732,185 discloses a method for cleaning a contact lens comprising establishing an electric field in a determined direction in a boric acid-EDTA buffer solution having pH 8 to 9 and immersing a contact lens in the solution to remove proteins from the contact lens by electrophoresis. When this method is carried out, proteins contaminated in the interior of a water-absorptive contact lens can be surely removed. However, the method requires that proteins should not be denatured and are ionized, and there are some problems in the method such that it takes a long period of time for the treatment. Also, according to this method, there are some problems such that a contact lens cannot be heated to prevent the thermal denaturation of proteins, and that boric acid does not impart suffient disinfecting effect to the contact lens.
U.S. Pat. No. 5,118,401 discloses a counter periodically changes the logical level of its output signal at 8 times during the disinfection cycle when an apparatus for applying a disinfectant solution containing 0 to 5% of hydrogen peroxide. However, when the content of hydrogen peroxide is 0% or so, disinfecting effects are not sufficiently imparted to a contact lens. Also, when hydrogen peroxide is used in the disinfectant solution, there is a problem such that strong stimulation is imparted to human skin.
On the other hand, as a method for disinfecting a water-absorptive contact lens, a method comprising immersing the contact lens in a sodium chloride aqueous solution and generating hypochlorite by applying an electric current to the solution to disinfect the contact lens as disclosed in Japanese Unexamined Patent Publication No. 68454/1981 and Japanese Unexamined Patent Publication No. 153658/1982, a method comprising immersing a contact lens in an H.sub.2 O.sub.2 aqueous solution to disinfect the contact lens and decomposing the H.sub.2 O.sub.2 with a metallic catalyst, a reducing agent and an enzyme catalyst to make the solution harmless as disclosed in Japanese Unexamined Patent Publication No. 38559/1983, Japanese Unexamined Patent Publication No. 68858/1985 and Japanese Unexamined Patent Publication No. 217333/1985, and the like have been known other than the above-mentioned method for disinfecting a contact lens comprising boiling the contact lens to disinfect.
However, according to the method of generating hypochlorite (a hypohalite) by electrolysis, it takes a long period of time for the natural disappearance of hypochlorite remaining in a treating vessel after disinfecting, and the procedures are also complex because the hypochlorite should be reduced so that hypochlorite does not remain in a water-absorptive contact lens. Furthermore, when the above procedures are applied to a colored contact lens or a dye-marked contact lens, there are some problems such that decoloration or discoloration of the contact lens occurs during the treatment.
Also, according to the above-mentioned method of using an H.sub.2 O.sub.2 aqueous solution, besides taking a long period of time for the treatment since H.sub.2 O.sub.2 remaining in the water-absorptive soft contact lens should be decomposed, stimulation such as smarting of eyes occurs if H.sub.2 O.sub.2 remaining in the interior of the water-absorptive contact lens is not completely decomposed. Therefore, the above method is not a suitable disinfecting method.
In consideration of the problems of the above-mentioned prior art, a method for solving the problems has been found (Japanese Patent Application No. 114463/1990).
This method is a method for cleaning and disinfecting a contact lens, comprising immersing a soft contact lens electrolyte solution in which a hypohalogenous acid salt is not generated by electrolysis, and applying a direct current to the solution to remove protein from the surface of the contact lens and/or the interior thereof, and at the same time increasing the temperature of the treating solution to a temperature within the range of 80.degree. to 100.degree. C. to heat and disinfect the contact lens. More concretely, the above-mentioned method utilizes the electrophoresis, that is, the nature that a colloidal, electrically charged protein is moved from the contact lens to an anode or cathode by applying a direct current to the electrolyte solution when the protein is not denatured and is liberated in the electrolyte solution. This method comprises cleaning a contact lens by moving protein adhered to or existing inside of the contact lens, which is immersed in the electrolyte solution, to the outside of the contact lens, and decomposing and removing the protein with the aid of peroxide generated by the electrode reaction, and at the same time heating the electrolyte solution to a temperature of 80.degree. to 100.degree. C. and disinfecting the contact lens with the aid of the application of electric current.
However, the upper limit of the concentration of peroxide generated in the above-mentioned method is at most 2 to 3 ppm, and the concentration is lowered within 5 minutes from the beginning of the application of electric current. Therefore, with many stains such as protein which is denatured and adhered to the contact lens, cleaning effect becomes sometimes insufficient.
In recent years, since a domestic power source for boiling and disinfecting a water-absorptive soft contact lens and the like cannot be sometimes used while traveling, the development of a method for easily disinfecting and cleaning a contact lens using a little electric power has been desired.
The present invention has been accomplished in consideration of the above prior art.
An object of the present invention is to provide a method which can easily, effectively and safely clean a contact lens.
Another object of the present invention is to provide a method of cleaning a contact lens, giving no wrong influences to eyes, having safety for eyes and excellent detergency, by which protein which is adhered to or existed in the interior of the contact lens can be removed.
A further object of the present invention is to provide a method for cleaning and disinfecting a contact lens for which only a low electric power is required from the viewpoint of electric safety.
A still further object of the present invention is to provide a method for electrically treating a contact lens, which can be preferably applied to a portable contact lens treating apparatus by using a battery.
These and other objects of the present invention will become apparent from the description hereinafter.